Drilling rig safety device



P. E. LEHR ET AL DRILLING RIG SAFETY DEVICE 2 Sheets-Sheet 1.

Filed Aug. 16, 1954 INVENTORS P. E. LEHR RC, MC NEILL & Hf? THEIR AGENT RE. LEI-IR R.C. Me NEILL THEIR AGENT 2 Sheets-Sheet 2 INVENTORS P E LEHR ET AL DRILLING RIG SAFETY DEVICE 4 7 4 KKK 3) Filed Aug. 16, 1954 DRILLING mo SAFETY DEVICE Paul Edward Lehr, Brett, and Robert Clark McNeil], Long Beach, lCalifi, assignors to Shell Development Company, New York, N. Y., a corporation of Delaware Application August 16, 1954, Serial No. 450,086

4 Claims. (Cl. 254-145) The present invention relates to apparatus for drilling oil and gas wells and pertains more particularly to a device adapted to be secured to the fall lines of a drill rig for releasing in a controlled manner the dead end of the fall lines from its anchored position as a safety measure to prevent damage to the drill rig.

In the drilling of oil and gas wells, crown block accidents occur from time to time either due to human error or to failure of equipment. These accidents occur when the traveling block positioned at the lower end of the fall lines of a hoist system on a drill rig is hoisted so fast or so far that it is run into the crown member, or crown block, which is fixedly secured at the top of a drill rig or mast. While such errors are mainly due to human error on the part of the operator controlling the hoist system, other factors contribute to this accident hazard, such as, for example, foggy weather, a lack of clearance within the rig when pulling long stands of pipe, changes in the length of tubing or rod joints, etc. Crown accidents occur infrequently and minor ones are usually nullified by the presence of a rubber bumper under the crown member at the top of the rig. However, severe damage, injury, and loss of life have occurred in the past as a result of severe crown accidents.

Various devices have been developed to prevent crown accidents or give warning thereof. In one system, an electronic eye is mounted near the top of the drill rig, so that the light beam to a photoelectric cell is intercepted by the traveling block just before it contacts the crown block, which causes a bell to ring a Warning to the rig crew. This device is merely a warning system and does nothing to prevent the crown accident itself. In another system, the hoist apparatus is arranged so that the clutch on the drive shaft of the hoist is disengaged and the brake is thrown on when the traveling block is about to run into the crown block. This systern was found to be unsatisfactory in that too much time was consumed before the hoisting system was completely stopped and the inertia energies thereof dissipated.

It is therefore a primary object of this invention to provide an apparatus adapted to be mounted in the hoist system of a drill rig to prevent injury to the hoist system whenever a traveling block is inadverently run too close to the crown block by the operator in charge.

Another object of this invention is to provide an apparatus adapted to be secured to the fall lines of a drilling rig hoist system for instantaneously increasing the length of the fall lines in the event of a crown accident.

A further object of this invention is to provide an apparatus secured to the fall lines of a drilling rig hoist system to dissipate the inertia energies of the hoisting system.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

Figure 1 is a diagrammatic view illustrating the ap- States Patent paratus of the present invention mounted at the base of a drilling rig and secured to the hoisting system of said rig.

Figure 2 is a longitudinal view, partly in cross-section, of the safety device of the present invention.

Figure 3 is an enlarged crosssectional view showing the detail of the piston head operating within the apparatus shown in Figure 2.

Referring to Figure 1 of the drawing, a drill rig 11 is shown positioned above an operating platform 12. The hoist system of the drill rig comprises a crown block 13, rotatably secured to the top of the rig 11, a traveling block 14 carried by fall lines 15 which are strung from the crown block 13, and a power driven hoist drum 16 for reeling and unreeling the live end of the cable 17 as the traveling block 14 is raised and lowered within the drill rig. Instead of being anchored to the operating platform 12, or to a leg of the drill rig 11, the dead end of the cable 20 is secured by suitable clamp means 21 to the upper end of the safety device of the present invention, as shown. A ring 23 on the lower end of the present safety device 22 is fixedly anchored to another ring 24 or anchoring bolt in the operating platform 12 to prevent vertical movement of the lower end of the safety device 22. While for ease of illustration the present safety device is shown as being mounted for use in a conventional drilling rig,,it is to be understood that said device is especially useful in a drilling mast of a well-servicing unit where the normal clearance between a traveling block and a crown block is generally much less than in a conventional drilling rig, and thus is more readily subject to crown accidents.

Referring to Figure 2 of the drawing, the present safety device comprises an elongatedhigh pressure tubular housing 25 having mounted there in for sliding axial movement a piston 26 having a tubular piston rod 27 of a length such that one end of the rod 27 extends out of the top of the tubular housing 25. The top of the piston rod 27 is closed by suitable cap means 28 having a hook or ring 29 mounted on the top thereof to which the dead end 20 of the cable in the hoist system shown in Figure 1 may be attached. The diameter of the piston rod 2'7 is smaller than the inner diameter of the tubular housing 25 so that an annular space 30 is formed between the outer wall of the piston rod 27 and the inner wall of the housing 25.

As shown in Figure 3 of the drawing, the piston 26 may be mounted on the lower end of the piston rod 27 in screwthreaded engagement therewith, and fixedly secured in position by a piston lock washer 35 (Figure 3). The piston 26 is preferably provided with a plurality of circumferential grooves 34 in which suitable sealing elements such as 0 rings 35 and/or leather gaskets 36 may be mounted. The head of the piston 26 is provided with an axial passageway 37 which is in communication with one or more radial passageways 38 drilled in the piston head to permit the flow of fluid therethrough. The axial passageway 37 has a check or relief valve 39, preferably of the ball-type, mounted therein for limiting the flow of fluid through said passageway in one direction.

The tubular head that closes the top of the tubing housing 25 may be made of two sections 41 and 47 forming a housing for the packing assembly which constitutes the fluid-tight seal between the top of the tubular housing 25 and the outer surface of the piston rod 27. The head section 41 is screw-threaded to the top of the tubular housing 25 and is provided with an inwardly extending.

flange 43. The flange 43 forms on its lower side an extending shoulder stop which limits the upward travel of piston 26, while the upper side of the flange serves as a base on which rings of packing 44 may be positioned. A packing gland bushing 45 and the packing gland 46 surround the piston rod 27 and are mounted above the rings of packing 44. The entire packing assembly, constituting elements 44, 45 and 4.6, is held in place by head section 42 which is screw-threaded to head section 41 so that an inwardly formed shoulder 47 on head section 42 contacts and maintains pressure against the top of the packing gland 46.

The head section 41 at the top of the tubular body member 25 which closes the annular space 30 is provided with fluid discharge port means 50 having suitable coupling or flange means 51 whereby .a flanged by-pass conduit pipe 52 may be secured so as to be in fluid communication with the interior of the tubular housing 25. The other end of the by-pass conduit 52 is flanged to a flange 53 surrounding the inlet port 54 of a fluid pressure relief valve 55. Any suitable type of spring-loaded relief valve 55 may be employed. The valve 55 illustrated is of general construction being provided with valve closure means 56, valve stem 57, spring 58, spring follower plate 59, and adjustment screw 60 for adjusting the compression of the spring 58 which tends to maintain the valve closure means 56 in a normally closed position. A flange 61 surrounding the discharge port 62 of the relief valve 55 is suitably connected, as by bolts 63, to the bottom of the tubular body member 25 whereby the interior of the valve 55 is in communication with the bore of the tubular body member 25, below the piston 26.

The top of the piston rod 27, or the cap means 28 secured thereto, is provided with one or more holes 66 of a size to contain a shear pin 67. Another set of holes (not shown) extend through the wall of the top section 42 of the tubular body member 25 so as to be in register with the holes 66 in the top of the piston rod 27 when the piston rod is in its retracted or inoperative position, as illustrated. If desired, a circular overhanging shear pin retainer 68 may be secured to the top of the head section 42, as by bolts 69, to retain the shear pins 67 in place. Usually, however, the normal tension on the ring 29 caused by the dead end of the hoist cable is suflicient to prevent the shear pins 67 from slipping out of their holes 66. The cap means 28 at the top of the hollow piston rod may also be provided with a fluid passageway 79 normally closed by a cap 71. When needed, additional fluid may be added to the system through this passageway 70. During normal operations, the entire apparatus including the tubular housing 25, piston rod 27, by-pass conduit 52 and relief valve 55 are filled with a hydraulic fluid, such as oil.

During drilling operations the present drilling rig safety device is mounted in a manner illustrated in Figure l of the drawing. In the event that the traveling block 14 is pulled up against the crown block 13 so as to cause a crown accident, the pull on the cable 17 and the dead end thereof 20 rises to a value above that (say, 30,000 pounds force) at which the shear pins 67 will shear. Upon the shearing of the pins 67, the piston rod 27 which is fastened to the dead end of the line 20and the piston 26 are drawn upwardly to force the hydraulic fluid contained in the annular space 30 and in the by-pass conduit 52 around the by-pass line and through the relief valve 55. The valve 55 is set at an operating pressure so that the inertia energies of the hoist system are absorbed as the fluid is forced through the valve against the back pressure. Thus, the present safety device acts as a hydraulic shock absorber of a relatively constant pressure type which is used to dissipate energy over its stroke in one direction. The relief valve 55 operates at constant pressure and is substantially independent of flow velocity or piston speeds as would be encountered in employing an orifice. The valve 55 is provided with suitable adjustment means 69 so that the back pressure .of the valve may be adjusted as needed depending upon changing operating or drilling conditions.

The design of the present hydraulic shock absorber safety device is such that it may be installed adjacent one leg of a rig or mast, or on the operating floor. This is especially advantageous when the present device is being used with a portable mast in that the available travel space within the mast for the traveling block is not reduced and secondly, when the mast has been folded on a truck for traveling and is lying horizontally, the added weight of the present safety device is supported upon the rear of the truck rather than on the critically loaded front axle.

After a crown accident has occured and the present safety device has been actuated, the piston 26 and piston rod 27 are readily restored to their retracted position due to the installation of the ball-type check valve 39 in the axial passageway in the piston head 26. Thus when the piston 26 and rod 27 are manually pushed back into the tubular body member 25, fluid contained within the body member 25 is forced upwardly through passageway 37 past valve 39 and through passageways 38 into the annular space 30 between the piston rod 27 and the body member 25. When the piston 26has been fully retracted, a new set of shear pins 67 are installed in their holes 66. The number, size and/or material of the shear pins is determined by the normal weight that is expected on the dead end of the line 20 of the hoist system and the maximum force that it is desired to have on the cable 17 of the hoist system before the shear pins are fractured.

We claim as our invention:

1. A drilling apparatus comprising a drill rig, a crown block, a traveling block, a hoist drum, a hoist cable strung from said drum to said crown block and traveling block, the dead end of said cable anchored to a constant pressure type hydraulic shock absorber fixedly secured to said drill rig near the base thereof, said hydraulic shock absorber being adapted to dissipate energy over its stroke in one direction, said hydraulic shock absorber being filled with a hydraulic fluid and comprising a fixed tubular body memher, a piston and piston rod slidingly mounted in said body member and extensible through the top thereof, means for securing the dead end of said cable to the top of the piston rod, by-pass conduit means in communication between the opposite ends of the body member on opposite sides of said piston, relief valve means in said bypass conduit means, and shear pin means extending through the Wall of said body member and into said piston rod for normally maintaining said piston rod' in a retracted inoperative position within said body member, said shear pin means being adapted to shear and allow the piston rod to be substantially withdrawn from said body member when an excessive force is applied to said cable.

2. A drilling apparatus comprising a drill rig, a crown block, a traveling block, a hoist drum, a hoist cable strong from said drum to said crown block and traveling block, the dead end of said cable anchored to a constant pressure type hydraulic shock absorber fixedly secured to said drill rig near the base thereof, said hydraulic shock absorber being adapted to dissipate energy .over its stroke in one direction, said hydraulic shock absorber being filled with a hydraulic fluid and comprising a tubular body member fixedly secured to said drilling rig, a piston and piston rod slidingly mounted in said body member and extensible through the top thereof, means. for securing the dead end of said cable to the top of the piston rod, by-pass conduit means in communication between the opposite ends of the body member on opposite sides of said piston, hydraulic pressure relief'valve means in said by-pass conduit means, and shear pin means extending through the wall of .said body member and into said piston rod for normally maintaining said piston rod in a retracted inoperative position within said body member, said shear pin means being adapted to shear and allow a major portion of the piston rod to be withdrawn from said body member when an excessive force is applied to said cable.

3. A drilling apparatus comprising a drill rig, a crown block, a traveling block, a hoist drum, a hoist cable strung from said drum to said crown block and traveling block, the dead end of said cable anchored to a constant pressuretype hydraulic shock absorber fixedly secured to said drill rig near the base thereof, said hydraulic shock absorber being adapted to dissipate energy over its stroke in one direction, said hydraulic shock absorber being filled with a hydraulic fluid and comprising a tubular body member having a piston chamber formed therein, a piston and piston rod slidingly mounted in said body member and extensible through the top thereof, said piston rod having an outside diameter less than the inner diameter of said tubular body member whereby an annular space is formed between said rod and said body member, means for securing the dead end of said cable to the top of the piston rod, by-pass conduit means parallel to and in communication between the opposite ends of the body member on opposite sides of said piston, adjustable springloaded hydraulic pressure relief valve means in said bypass conduit means, and shear pins extending through the wall of said body member and into said piston rod for normally maintaining said piston rod in a retracted inoperative position within said body member, said shear pins being adapted to shear and allow the piston rod to be substantially withdrawn from said body member when an excessive force is applied to said cable.

4. A drilling apparatus comprising a drill rig, a crown block, a traveling block, a hoist drum, a hoist cable strung from said drum to said crown block and traveling block, the dead end of said cable anchored to a constant pressure type hydraulic shock absorber fixedly secured to said drill rig near the base thereof, said hydraulic shock absorber being adapted to dissipate energy over its stroke in one direction, said hydraulic shock absorber being filled with a hydraulic fluid and comprising a fixed tubular body member having a piston chamber formed therein, a piston and piston rod slidingly mounted in said body member and extensible through the top thereof, means for securing the dead end of said cable to the top of the piston rod, by-pass conduit means in comunication between the opposite ends of the body member around said piston, hydraulic pressure relief valve means in said by-pass conduit means, shear pins extending through the Wall of said body member and into said piston rod for normally maintaining said piston rod in a retracted inoperative position within said body member, said shear pins being adapted to shear and allow the piston rod to be substantially withdrawn from said body member when an excessive force is applied to said cable, and conduit means through said piston in communication with the space Within said body member on opposite sides of said piston, check valve means in said piston conduit means for permitting flow therethrough when said piston rod is returned to its retracted inoperative position.

References Cited in the file of this patent UNITED STATES PATENTS 1,020,445 Potter Mar. 19, 1912 1,134,224 Phillips Apr. 6, 1915 2,109,297 McMurry et al. Feb. 22, 1938 2,241,274 Severson May 6, 1941 2,401,748 Dillon June 11, 1946 2,564,457 Wilson Aug. 14, 1951 2,670,925 Des Champs Mar. 2, 1954 

